When an automobile collides with another automobile or a building, there may be a risk that the driver is brought into a secondary collision with the steering wheel due to inertia. In recent passenger vehicles, in order to prevent the driver from getting injured in case such an accident occurs, impact absorbing steering column apparatuses are widely used together with seat belts and air bags. While there exist various types of impact absorbing mechanisms which are adopted for the impact absorbing steering column apparatuses, a double-tube type steering column apparatus is generally used in which a steering column collapses (decreases in length) together with a steering shaft when the driver has a secondary collision so as to absorb impact energy during the collapse.
The impact absorbing steering column apparatus of this type includes, for example, an outer column supported on a vehicle body side bracket, an inner column slidably fitted in the outer column and an impact energy absorbing means interposed between the outer column and the inner column, and when an axial load of a predetermined value or greater is applied to the steering column apparatus, the inner column slides into the outer column, whereby the impact energy is absorbed by the impact energy absorbing means as the inner column slides into the outer column.
In contrast, in an automotive steering system, it is desirable that the position of the steering wheel can be adjusted in accordance with builds and driving postures of individual drivers as the steering wheel is used (operated) by an unlimited number of drivers. With a view to satisfying such a demand, a tilt mechanism and a telescopic mechanism are used on an increasing number of trucks as well as passenger vehicles.
The tilt mechanism is a mechanism for adjusting vertically the position of a steering wheel and is made up of a tilt pivot for supporting a steering column in such a manner as to allow for a tilt and a tilt holing means for holding the steering column at a desired position (tilt angle). In addition, the telescopic mechanism is a mechanism for adjusting the position of the steering wheel in a longitudinal direction (an axial direction of a steering shaft) and is made up of a telescopic portion of double-tube type for use for allowing for a telescopic movement of the steering shaft and a telescopic holding means for holding the steering shaft at a desired position (telescoped amount).
In Japanese Patent Unexamined Publication JP-A-11-291922 and Japanese Utility Model Registration No. 2584258, in a steering column apparatus including a tile mechanism and a telescopic mechanism, impact energy is designed to be absorbed by an impact energy absorbing means.